The study is designed to measure optic disc cupping in photographs of the optic discs obtained on 2990 diabetic persons who participated in the Wisconsin Epidemiologic Study of Diabetic Retinopathy in 1980-1982 and who will be seen again in 1984-1986, and in 381 non-diabetic subjects who were and will be seen during the same time intervals. Measurements will be made using a standardized technique. Double gradings will be performed and graders will be masked as to the diabetes status of the subjects. Gradings will be correlated with intraocular pressures that were recorded at the time of fundus photography. The influence of possible confounding variables will be assessed. The longitudinal data will permit a quantitative estimate of the predictive value of intraocular pressure for change in optic disc cupping. Comparing rates in the diabetic persons and non-diabetic persons in this study and in other populations will allow us to determine whether diabetic persons demonstrate an increased prevalence of greater optic disc cupping. A sample of diabetic persons and an age matched group of non-diabetic persons will have Goldmann visual field testing. Examination of the visual fields, intraocular pressure and stereophotographs of the optic nerves will be assessed by two ophthalmologists independently, and in masked fashion. This will provide an estimate of the risk of glaucoma in diabetics as compared with non-diabetic persons.